SQL query question

Do all four of these tables have the same schema?  If yes, better to do a UNION ALL if you want to make sure that the row counts in 1+2+3+4 = what is inserted into the target_table, and just UNION if you want to eliminate duplicates between 1, 2, 3, and 3.

INSERT INTO target_table(id, a, b, c)
SELECT id, a, b, c
FROM temp_1
UNION ALL
SELECT id, a, b, c
FROM temp_2
UNION ALL
SELECT id, a, b, c
FROM temp_3
UNION ALL
SELECT id, a, b, c
FROM temp_4

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Without sample data and expected result I would be guessing my way through an answer to this broad question.

Maybe Jim has guessed right?

Sample data and table schemas are needed to we can provide a better solution.

My apologies for being not clear. I have four tables. Each tables have only one column common: ProductID. Each temp table  contains only part of data (usually 6 columns) that should contain Perm table. The all tables belong to the same schema. My Insert query looks somewhat like this:

INSERT INTO PermTable (ProductID, value1, value2, value3, value4) SELECT t1.ProductID, t1.Value1, t2.Value2, t3.Value3, t4.Value4 FROM Temp1 t1 INNER JOIN Temp2 t2 ON t1.ProductID = t2.ProductID INNER JOIN Temp3 t3 ON t1.ProductID = t3.ProductID LEFT OUTER JOIN Temp4 t4 ON t1.ProductID = t4.ProductID

It works when ProductID is unique but if there is 2 records with the same ProductID in Temp Tables I will get four records in Perm table.

If the is a repeated product id in one of the temp tables, what is supposed to happen?

for example, let's say it is

table2
productid value2
12345        12345.6
12345         23456.7

i.e. if there is a difference in value2 (as shown) what would you expect to happen?

I wanted to ask a similar question;
- What's a duplicate record? Rows with same ProductID and Value? Or only same ProductID?
- If it's only same ProductID, which value need to be selected? MIN? MAX? AVG? Other?

In my cases I have two records with the same ProductID in Temp1, Temp2 tables. One record in Temp3 and none in Temp4. When I executed my query it inserted into Perm table not two but four records. So Perm table looks like that:

Perm
productid value2
12345        12345.6
12345         23456.7
12345        12345.6
12345         23456.7

As been asked above:

i.e. if there is a difference in value2 (as shown) what would you expect to happen?

- If it's only same ProductID, which value need to be selected?

I need both values. But I need TWO records which is correct NOT FOUR records I am getting that is wrong.

I tried it but I got only one record but I have to get two.

Please provide samples for the 4 tables.
and the expected result.

This truly is the fastest way to resolution.